Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

085
FXUS63 KLOT 290336
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
936 PM CST Sun Dec 28 2025

.KEY MESSAGES...

- A wind advisory is in effect due to the expected powerful
  winds, gusting over 50 mph at times, tonight into Monday
  morning areawide. Gusts may reach 55 to 60 mph at times in
  northern Porter County, Indiana as stronger winds move off of
  Lake Michigan.

- Wind whipped snow showers and flurries are expected late
  tonight through Monday morning, especially north of I-88/I-290
  where locally an inch or two of accumulation could result in
  hazardous travel. A Winter Weather Advisory has been issued
  for far northern Illinois (Ogle, Winnebago, Boone, northern
  DeKalb, McHenry, northern Kane, northern Cook, and Lake
  Counties).

- Temperatures will continue to plummet through tonight. Expect
  wind chills close to zero Monday morning.

&&

.UPDATE...
Issued at 936 PM CST Sun Dec 28 2025

In coordination with WFO MKX, opted to issue a Winter Weather
Advisory for far northern Illinois, mainly north of I-88. In
these areas, localized accumulations of 1-2", the very strong
westerly winds, and patchy ice from lingering moisture freezing
should contribute to hazardous travel being more prevalent in
the advisory counties. With snow expected to be falling into
and/or through the morning commute as the strong winds continue,
the added concern for impacts to the morning commute warranted
the addition of a Winter Weather Advisory.

Expect lighter snow showers and flurries for most of the area
through the late evening, followed by more widespread falling
snow into Monday morning. Updated forecast has locally 1-2" of
snow in the advisory counties, which may be enough to cause an
additional hazard from areas of blowing and drifting snow,
particularly on north to south roads in open/exposed areas.

For northwest Indiana, there had been concern for considering an
upgrade to High Wind Warning for areas near the lake in Porter
County. Still can`t rule out gusts to 60 mph near the lake, but
confidence in occurrence and frequency wasn`t high enough based
on latest forecast guidance to upgrade to a warning. On the
other hand, northeast Porter County may need to be included in a
Winter Weather Advisory as wind blown lake effect snow develops
after the overnight through Monday morning system snow.

Castro

&&

.DISCUSSION...
Issued at 240 PM CST Sun Dec 28 2025

Through Monday:

Heavy rain and thunderstorms are on a break here locally during
the early afternoon after an eventful morning. Widespread light
to moderate rain impacted most of our CWA and we saw a corridor
of mostly sub-severe thunderstorms near and south of I-80. One
lone severe storm managed to produce some noteworthy wind damage
in Livingston County. We also received a handful of reports of
street flooding. It appears that over half an inch of rain fell
around a big majority of our CWA this morning with a sizable
corridor of 1-2" near and south of I-80. Here in Romeoville,
we`ve received over 1.1" since this morning.

Lighter, densely scattered showers now continue near and north
of I- 80 as of around 2 PM as the warm front continues to push
north ahead of the approaching cyclone. The MUCAPE reservoir
has not kept up with the front on its northward progression,
which explains the absence of thunder now.

Down into central IL, we`ve seen convective activity quickly
develop along the storm`s strengthening cold front. Embedded
severe convection is crossing the Illinois River near Peoria as
of 2 PM. Latest SPC mesoanalysis shows between 500 and 1000 J/kg
of surface- based instability is available across central IL
and stretching into our far southern CWA along and ahead of the
line. This comes as temperatures have warmed to near 70 degrees
and dewpoints into the lower 60s in central IL within the
storm`s warm sector. It also depicts 30 kt of 0-1 km shear along
this line and 50 to 60 kt of 0-3 km shear. This line will race
toward the east at 50 to 60 mph through the remainder of the
afternoon. Expectations are for thunderstorm coverage to fill in
along the front into mid-afternoon as the accelerating warm
conveyor continues to transport moisture and instability
northward. The better part of the Chicago metro could be in for
additional elevated storms near and south of the storm`s triple
point. But the more appreciable ingredients for severe
convection still look to favor areas roughly along and east of
I-55 and south of I-80 during the latter half of the afternoon.

Primary severe hazards will be damaging wind gusts to 60 to 70
mph and a few tornadoes. The threat for both has increased now
that surface-based storms are basically certain. A Tornado Watch
was recently issued from SPC in this corridor. Very heavy
rainfall is also possible along this line, but given the
progressive nature of the front, not really anticipating many
flooding issues outside of areas that saw problems earlier
today; those could be resurrected by the added rainfall. The
window for severe convection in our area looks rather brief,
roughly 3 to 6 PM. Over any given area, the severe threat will
only last a handful of minutes. The line will push east of the
CWA by 6 PM.

Winds will ramp up very quickly in the wake of this system/cold
front late this afternoon and evening. Most of the CWA should
be looking at gusts out of the west at 30 to 35 mph by dusk
building to 45 to 50 area-wide by the end of this evening. Such
winds are expected through the night and into early Monday, with
steady but very gradual easing expected during the morning and
afternoon. No changes were made to the going Wind Advisory. An
upgrade to a High Wind Warning was considered in Porter County,
IN where there are concerns for a period 60+ mph winds to
protrude inland off the lake. While this looks to be confined to
only a handful of miles inland from the shore, these sorts of
winds would be moving over I-94 and other major arterials along
the lakeshore possibly during portions of the morning commute.
Confidence wasn`t quite there to warrant upgrading yet, but
considerations will still be made.

Also in the wake of the front, temperatures will drop like a
rock this evening and tonight, as many as 20+ degrees in just a
few hours. It`s tough to say the extent of impacts we`ll see
from any flash freezing, but at least some slick spots on roads
appear likely to form. Any lingering puddles or ponding will
freeze, but hopefully these will mostly be found 26off of
roadways. The strong winds this evening should help dry roads
off before freezing over. However, even if no snow on the roads,
be aware that areas could be slippery late tonight into
tomorrow. Also prepare for a much colder day with morning winds
chills near and below zero, and in the single digits above zero
during the afternoon.

Snow showers are expected to wrap around the low to the north
and fall on the CWA this evening into Monday. The best chances
to see true snow showers through most of tonight will be north
of I-80 where flurries will be favored farther south. The better
push of snow showers appears to come late during the overnight
and into Monday morning as a secondary boundary pushes across.
Forecast soundings depict a few hour window where added forcing
from this wave will interact with a rather deep DGZ presence and
could churn up some moderate snow at times, especially in our
northern CWA and around Lake Michigan. The windy conditions will
only make matters worse on the roads leading to blowing snow
and poor visibility. Even lighter snowfall will bring about
hazardous travel conditions. Be prepared for sudden changes in
visibility in snow tonight and Monday morning, including during
the commute. Snow may linger into the afternoon, mainly around
the lake and into northwestern IN with flurries possible
elsewhere, but most of the area will see an end to the impactful
snow showers sometime during the morning. Guidance favors
around an inch of accumulation up near the WI state line and a
couple to several tenths elsewhere around the area.

Doom

Monday Night through Sunday:

The upper level low that is driving this weekend`s weather will be
over Quebec by Monday night. Another upper level low is expected to
drop southward from Hudson Bay Monday night through Tuesday. While
these two upper level lows phase with each other, impacting the
weather out east, it will send a series weak disturbances extending
back over Lake Michigan that could provide a couple additional
rounds of wintry precipitation. Unfortunately, models are showing
little agreement providing lower confidence in the details.

The first weak disturbance drops southward out of Canada on Tuesday.
The Euro ensemble has a surface low in south-central Canada dropping
into northern Minnesota before weakening as it moves from the
Minnesota arrowhead to Michigan`s western mitten. The GEFS meanwhile
has a weaker wave and a more eastern track. For now, kept snow out
of the forecast. Maybe some flurries or light snow is possible
for areas closer to Lake Michigan, but unless models shift more
westward, dry conditions should prevail.

Models have shown some decent agreement that as the previously
mentioned upper lows phase around each other Tuesday night into
Wednesday, they will slowly retrograde westward into Ontario with
a strengthening 300 mb 100+ knot jet and a reflected deepening
surface cyclone. With a weak mid level wave dropping southward, a
surface cold front is expected to pass over the area on Wednesday
with much more robust cold air advection behind the front. No
changes were made to the PoPs as latest NBM run keeps chances for
snow for much the area. There is still plenty of model
disagreement on exact timing and snow amounts. And while current
indicators are that it does not have a signature of a major snow
storm, it could provide a coating on the ground. Holiday revelers
may expect some snow falling down as 2025 runs out of time.

Temperatures will feel much more winter like through the week. As
northwest winds persist through Monday night into Tuesday morning,
single digits to low teens are expected in the morning with wind
chills at or just under zero degrees F. High temperatures are
expected in the 20s to just below freezing Tuesday and Wednesday.
New Years Day looks to be a chilly one as temps drop once again
behind the front. The NBM is suggesting solidly in the 20s for
highs, but that might be biased by the GFS/GEFS having no snow,
whereas the Euro suite is advertising highs in the teens (a likely
result "if" there is a coating of snow on the ground).

Temperatures are expected to climb slowly back into the upper 20s
and low 30s for the end of the week/weekend. There is a chance for
another winter system that could bring some more precip to the area,
potentially on Sunday, but models are not showing a lot of agreement
at this distance to have great confidence.

DK

&&

.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 523 PM CST Sun Dec 28 2025

Forecast concerns include...

Very strong/gusty westerly winds.
Light snow/blowing snow overnight/early Monday morning.

The cold front is east of the terminals ending the threat of fog
and thunder. There may be a few lingering showers for the next
hour or so with a lull in the precipitation through late
evening. Light snow is expected to develop in the early
overnight hours and continue through daybreak Monday morning.
The snow will be dry/fluffy and should be easily blown around.
Continued with light snow/blowing snow with this forecast.
Prevailing visibility will likely be in the 1-2sm range though
brief vis under 1sm is possible. This snow is expected to taper
off to flurries from west to east around and just after
daybreak.

West/northwest winds will steadily increase over the next few
hours with gusts into the 40kt range from mid evening through
mid morning Monday, then gusts will slowly diminish through the
afternoon and into the mid 20kt range by Monday evening.

Ifr cigs will lift to low mvfr this evening and then mvfr cigs
are expected to continue into Monday afternoon, scattering out
Monday evening. cms

&&

.MARINE...
Issued at 240 PM CST Sun Dec 28 2025

- Gale Warning in effect from 5 PM Sunday to 6 PM Monday from
  Winthrop Harbor IL to Gary IN.

- Storm Warning in effect from Gary IN to Michigan City IN, from
  6 PM Sunday to 3 PM Monday.

A powerful cold front will sweep across the lake late Sunday,
resulting in a rapid increase to gale force and storm force
west-southwest winds. As low pressure continues to rapidly
deepen near Lake Huron Sunday night into early Monday, westerly
winds will further increase. Confidence in occurrence and
duration of storm force speeds/gusts is highest for the
southeast portion of the lake.

Freezing spray will also be possible late tonight and continue
into Monday as air temperatures are expected to be in the lower
20s and possibly into the teens.

Doom

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory until 3 PM CST Monday for ILZ003-ILZ004-ILZ005-
     ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-
     ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103-ILZ104-ILZ105-
     ILZ106-ILZ107-ILZ108.

     Winter Weather Advisory until 3 PM CST Monday for ILZ003-
     ILZ004-ILZ005-ILZ006-ILZ008-ILZ011-ILZ012-ILZ103.

IN...Wind Advisory until 3 PM CST /4 PM EST/ Monday for INZ001-
     INZ002-INZ010-INZ011-INZ019.

LM...Gale Warning until 6 PM CST Monday for the IL nearshore waters.

     Storm Warning until 3 PM CST Monday for the IN nearshore
     waters.

&&

$$

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